In order to perform high-speed communication, a wide-band signal is inevitably required. In complying with such a request, communication schemes such as W-CDMA (Wide Band Code Division Multiple Access) and OFDM (Quadrature Frequency Division Multiplex) have been developed.
In radio communication devices adopting these communication schemes, detection of over output power of an amplifier or the like is sometimes performed. The purpose of the over-output detection is, for example, to cope with legal regulations, or to prevent damage due to thermal stress inside the devices.
In a configuration for amplifying a wide-band signal, the signal to be amplified is a signal associated with instantaneous variation. Therefore, when operating an amplifier the output power of which is defined, it is necessary to measure the average power of the amplifier. In addition, also when checking whether or not the output power from the amplifier is proper, it is necessary to measure not the instantaneous power but the average power.
The wide-band signal treated in the above-mentioned communication schemes is characterized in having a high peak-to-average power ratio. Therefore, in order to perform measurement of the average power, detection of over output power, and the like, some calculation function is required.
That is, in order to measure the power of the wide-band signal, the instantaneous power variation needs to be averaged. For example, it is known that, in OFDM, the PAPR (Peak to Average Power Ratio) is about 10 dB. Therefore, the average power cannot be determined depending on whether or not the instantaneous power exceeds the defined power.
As an example of a method for measuring the average power, “Waveform Data Processing for Scientific Instrumentation”, CQ Publishing Co., Ltd., Shigeo Minami, pp. 86-97, Published in April, 1986 (Non-Patent Literature 1) discloses, in formula (5-15), a moving average calculation algorithm based on a recursive method using an average of multiple samples.